Switch browser side audio capture path to use base time primitives.

media/audio/audio_input_device.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/audio/audio_input_device.h"
 
 #include <stdint.h>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 317 matching lines @@
     LOG(ERROR) << message;
     capture_callback_->OnCaptureError(message);
   }
   last_buffer_id_ = buffer->params.id;
 
   // Use pre-allocated audio bus wrapping existing block of shared memory.
   media::AudioBus* audio_bus = audio_buses_[current_segment_id_];
 
   // Deliver captured data to the client in floating point format and update
   // the audio delay measurement.
+  // TODO(olka, tommi): Do something with |delay_timestamp|.

[o1ka, 2017/02/10 13:28:50]

Looking on TimeTicks::IsConsistentAcrossProcesses() method comment: how reliable
or inconsistent this value may be?

[o1ka, 2017/02/10 13:28:50]

Will we break anything if we leave it as "TODO"? Looks like we may need to
correct the delay basing on |delay_timestamp| and Now()?

[DaleCurtis, 2017/02/11 01:43:13]

Good question, looking at the implementations, this is always true on POSIX, but
on Windows depends on whether the high resolution timer is in effect or not. We
always use the high resolution timer when QPC is present, and a working QPC is
required for WASAPI delay information.

To your second question, no if you never do anything with this TODO, it won't
matter. I took a brief glance through the WebRTC capture code though and it
looked like it was trying to use the delay information relative to a timestamp,
so I thought this would be immediately useful.

If it's not useful or you don't plan to use it, I can remove it from this CL. In
fact this is the main reason I sent this CL early, to figure out if
delay_timestamp is actually interesting to you.

[o1ka, 2017/02/13 14:00:21]

Can we have this documented in the code?
I see, I need to do my homework on this - will be back tomorrow.

   capture_callback_->Capture(
       audio_bus,
-      buffer->params.hardware_delay_bytes / bytes_per_ms_,  // Delay in ms
+      base::TimeDelta::FromMicroseconds(buffer->params.delay).InMilliseconds(),
       buffer->params.volume, buffer->params.key_pressed);
 
   if (++current_segment_id_ >= total_segments_)
     current_segment_id_ = 0;
 }
 
 }  // namespace media